Mixing Valves Information
Mixing valves combine the flows of two or more inlets into a single outlet. They are extensively used in situations where specific concentrations must be combined and regulated. One of the most common uses for mixing valves is for controlling water temperature for circulation and faucet delivery in residential and commercial applications. Mixing valves are also used within the industrial market place for essentially the same purpose, but on a larger scale, for delivering water at a controlled temperature for HVAC and critical process and cleaning applications.
Types of Mixing Valves
Single handle mixer valves are the simplest of the mixing valve family. They produce a variable mixture of hot and cold water at a variable flow rate under control of a single manual handle.
Thermostatic mixing valves mix hot and cold water to produce a constant temperature in the presence of variable pressures and temperatures on the two input ports. These mixing valves provide precise and cost-effective temperature control. Even with sudden changes of inlet pressure and temperature to the valve, actuators within the valve minimize outlet temperature variations.
A tempering valve mixes hot and cold water to deliver hot tap water at a constant temperature. Tempering valves have a temperature sensitive element which adjusts the mix depending on the temperature of the incoming water flowing through the valve. The purpose of these valves is to maintain a high temperature in the water heater while providing scald protection for the user.
Steam-water mixing valves use a mixture of hot steam and cold water to provide a controlled hot water source. These valves use steam and water to provide hot water economically by blending steam and cold water quickly to the required user temperature. The outlet temperature can be adjusted to suit the user's temperature needs. These valves are not thermostatically controlled; in order to maintain a fixed hot water temperature the cold water pressure and flowrate must remain constant. If inconsistency occurs, users can easily regulate the temperature by turning the unit’s steam and cold water source valves. As a safety measure steam-water mixing valves shut off their steam source automatically if the cold water supply falls below a determined pressure for any reason. This prevents hazardous steam from exiting the unit and causing steam burns.
Some styles of mixing valves are designed with anti-scald protection to make sure that water is only dispensed within a safe temperature range. These are often used within hospitals, nursing homes, child-care facilities and other establishments where the user population requires additional protection.
The most common application for mixing valves is to combine, regulate and dispense hot and cold water received from two inlets. In most cases, a temperature sensitive element is employed, which expands or contracts depending upon the temperature coming into the valve. The element is tuned to dispense water within a certain temperature range, so its expansion and contraction will vary from the cold side to the hot side to maintain the desired temperature balance. Once the water temperature is balanced, it can be dispensed or it can be cycled back into the system.
Mixing valves can also combine and dispense fuels, dry solids, liquids, coolants and other chemicals. They are used extensively in industrial applications to perform a wide range of temperature and concentration control.
Additional applications include the following:
- Mixing valves are often found in HVAC service (for use in heating, ventilating, and/or air conditioning systems).
- Petroleum and pipeline operations, for use with petrochemicals such as engine oil, gasoline, diesel, and specialized fuels
- Chemical production facilities; power plants; food processing, for mixing operations in the food or beverage industry
- Medical service, for use with pharmaceutical chemicals or medical / surgical fluids
- Heavy industry, for applications in industries such as mining, quarrying, and mills